Power vehicles for carrying out diverse tasks are known. For instance, power lawn mowers are well known for use in turf maintenance. Such mowers may either be of the walk-behind or riding variety. One type of riding lawn mower that has grown increasing popular in recent years for both homeowners and professionals alike is the riding zero-turning-radius (ZTR) mower. While embodiments of the present invention are directed to control systems for use with a wide variety of riding or walk-behind vehicles, it will, for the sake of brevity, be described with respect to a ZTR mower.
A ZTR mower may typically incorporate a power source (e.g., internal combustion engine or electric motor) coupled to a continuously variable, e.g., hydraulic, drive system. The drive system may include left and right hydraulic motors coupled to left and right drive wheels, respectively. Power may be transmitted from the prime mover to the left and right hydraulic motors, e.g., via one or more pumps, to drive the left and right drive wheels independently. The rotational speed and direction of each drive wheel may then be controlled by an associated drive control lever or “stick” under the control of an operator. By manipulating the control levers independently, each drive wheel can be separately driven forward or backwards at varying speeds. As a result, the mower may be propelled forwardly or in reverse. By powering one wheel in the forward direction and slowing, stopping, or powering the opposite wheel in the reverse direction, the mower can execute a turn.
Each drive control lever may typically be positioned at any location between a neutral and a full forward (and generally a full reverse) position. A stop may define the full forward (and full reverse) position of each control lever.
During mower operation, the operator may seek to place the control levers in the full forward position as this position allows resting of the levers against the stop. This may offer the operator increased comfort, as well as reduce inadvertent lever movement as a result of, for example, traversal of undulating terrain. However, this full forward position may also result in a vehicle speed that is in excess of what is desired for some mowing tasks, e.g., bagging or mowing tall grass. Further, operators that are new to the operation of ZTR mowers may wish to limit the maximum potential speed of the mower until they have familiarized themselves with mower operation.
To reduce maximum mower speed, the operator may back the control levers away from the full forward position. However, this action prevents the operator from resting the levers against the stops. Alternatively, the engine throttle may be reduced. While throttle reduction is effective at reducing maximum vehicle speed (e.g., the speed at the full forward control lever position), it also reduces output to attached implements. For example, throttle reduction may reduce the rotational speed of the blades of an attached cutting deck, potentially reducing the cutting efficiently of the mower.
To address this issue, some mowers may provide a control lever travel limiter. The limiter may selectively restrict travel of each drive control lever by selectively interposing an intermediate stop to limit control lever movement to a position short of the full forward position. While the travel limiter may effectively limit the range of control lever movement, it does so by reducing lever travel, not lever sensitivity. Moreover, such travel limiting devices may be time consuming to adjust, complicated to operate, and/or difficult to engage without shutting down the mower.